TOTAL SHOULDER REPLACEMENT BY MAGNETIC ARTHROPLASTY

Permanent magnets offer a novel solution to the problem of shoulder im plant instability when the rotator cuff has been destroyed. We report a case of their use in a bb-year-old patient with a large proximal hum eral breast cancer metastasis. Humeral resection was below the deltoid insertion. The polyacetal device had samarium-cobalt magnets in the h umeral head. The glenoid component (the keeper in the magnetic circuit ) was made of titanium nitride-coated F17 stainless steel. The system breakaway force was ca. 40 N. At 24 months the shoulder was Free of pa in and stable, with an active range of movement of 30 degrees flexion, 45 degrees external rotation, and internal rotation to T8. The patien t could perform household tasks and drive an automatic car. Radiograph y showed no implant loosening or upward humeral head dislocation. Subs equently, the patient's condition deteriorated; at 33 months she was b edridden, and radiography showed dislocation of the humeral component.